This disclosure relates to the formation of an oxide coating foundation for promoting the adherence of a thermal barrier coating (TBC) to a substrate.
The high temperature exposure of nickel-based superalloys in turbine engines continues to increase. It is important that the nickel-based superalloy substrates be protected by thermal barrier coatings which enable their use in high temperature environments. Thermal barrier coatings provide a means to shelter the structural element, i.e. the turbine blade or vane, from the highest temperatures in the engine. However, oxidation of the metal surface of the substrate takes place as the thermal barrier coating is oxygen transparent. Metallic bond coats are added to the metallic surface of the substrate to form a reaction product of thermally grown oxide (TGO) of alumina between the bond coat and the thermal barrier coating topcoat. Formation of a sufficiently thick, adherent, and pure TGO scale is critical to both the oxidation protection of the superalloy and to achieve the adherence of the thermal barrier coating topcoat to the component.